Recent numerical control systems which mostly incorporate computers are called computerized numerical control (CNC) systems. The CNC system has a microprocessor and other components such as a tape reader, switches, lamps, and a servomechanism which are connected to the microprocessor through a bus line extending therefrom. The states of all of these components are detected from time to time by the microprocessor, which applies commands to these components to effect various operations according to a numerical control program. The numerical control program is ordinarily stored on a punched tape. Before the CNC system is operated, the punched tape is fed through the tape reader which then transfers the program from the punched tape into a random-access memory (RAM) in the CNC system. In some CNC systems, a numerical control program stored in a read-only memory (ROM) in the CNC system is transferred into the RAM.
Thereafter, numerically controlled operation is effected according to the numerical control program stored in the RAM.
The numerical control program in the punched tape or the RAM is stored in the form of a numerical control high-level language such as FAPT. Each time the numerical control program is executed, it is usually converted to a machine language applicable to the numerical control system by using a compiler stored in the numerical control system.
According to the prior art, when the numerical control program is executed, a tape editing area in the numerical control program must be used, and the processing time includes a time required to compile the numerical control program. Thus, the numerical control program cannot quickly be executed. Where a paper tape is employed to store a numerical control program, difficulty is experienced in keeping secrets since the numerical control program can easily be read by a human being.